Cable reeling drums

ABSTRACT

A cable reeling drum for reeling in the cable of a movable machine, such as an electrically driven crane, is driven by a motor through a slipping clutch which is designed to operate continuously over long periods without large scale variation of the transmitted torque. To this end the slipping clutch includes a pair of floating clutch plates, which are axially pressed against a clutch disc member. The clutch plates are driven by means of a spider secured to the clutch input shaft. The spider is connected to one or both clutch plates by means of two or more links which are connected to the spider and the clutch plate so as to permit free axial movement of the clutch plate. Ball joint connections between the links and the spider and clutch plate are provided for that purpose. The clutch disc is preferably channelshaped to provide improved cooling and the clutch plates and disc are enclosed within a casing forming the output member of the clutch, the casing protecting these parts from dirt and water.

United States Patent Mann Dec. 25, 1973 CABLE REELING DRUMS [75]Inventor: .lohn Brien Mann, Calverton, 'f' Exami7er Manuel AmonakasEngland Assistant ExammerRandall Heald Att0rney--E. F. Wenderoth et al.[73] Assignee: Metropolitan Tool and Products Limited, Nottingham,England 221 Filed: Sept. 14, 1972 [571 ABSTRACT [21] Ap NQ,: 288,981 Acable reeling drum for reeling in the cable of a movable machine, suchas an electrically driven crane, is driven by a motor through a slippingclutch which is [30] Fore'gn App-Imam) Pnomy Data designed to operatecontinuously over long periods Sept. l7, I971 Great Britain 43567/7lwithout large scale variation 0f the transmitted to que To this end theslipping clutch includes a pair of float- U-S' Cl. C, clutch plates areaxially pressed against a 192/7018, 192/111 3 clutch disc member. Theclutch plates are driven by Int. Cl. means of a spider ecured to theclutch input haft of Search C, R, The spider is connected to one orclutch plates 192/1 l 1 48-3, 70-l8 by means of two or more links whichare connected to the spider and the clutch plate so as to permit freeReferences Cited axial movement of the clutch plate. Ball joint connec-UNITED STATES PATENTS tions between the links and the spider and clutchplate 1,887,355 11 /1932 Kra'nick 64/30 R are Pmvided for that P Theclutch disc is P 2,306,730 12 1942 Holmes 64/30C erably Channel-Shapedto Provide improved Cooling 2,771,977 11/1956 Uher 1 192/111 B and theclutch plates and disc are enclosed within a 2,864,481 12/1958Strecker... 192/111 B casing forming the output member of the clutch,the 3,l05,37l lO/l963 Forrest 64/30 C asing protecting these parts fromdirt and water FOREIGN PATENTS OR APPLICATIONS 10/1956 ltaly' 192/7018 9Claims, 7 Drawing Figures PATENTEI] DEC 2 5 I975 SHEET 2 BF 6 PATENTED[15225 ms 3380.538 SHEET 3 [If 6 PATENTEDBEBZS I975 3780.538

SHEET 5 [IF 6 P TENIEnmzs I975 3.780.538

SHEET 8 OF 6 I I H o I CABLE REELING DRUMS This invention relates tocable reeling drums, especially those of the type on which electricalcable or flexible pipes or hoses may be wound.

Where machines which travel along a track, such as a crane or a gantry,require to be supplied with electric power from a fixed outlet, avariable length of cable is needed to extend betweenthe machine and theoutlet. It is convenient to have a cable reeling drum to pay out andreel in cable when the machine moves so as to avoid kinking the cablewithout applying undue tension. The drum may be stationary but ispreferably mounted on the machine.

It has been proposed previously to utilise a motordriven cable reelingdrum in which a slipping clutch is arranged in the drive between themotor and the cable drum. The motor is driven in such a direction thatthe drum will wind in slack cable and keep the cable under tension whenthe machine is stationary.

In one known arrangement the motor drives the cable drum through a wormand worm wheel, the worm wheel driving a clutch connected to the cabledrum. The worm wheel and friction discs of the clutch run in an oil bathlt has been found that with this arrangement the dissipation of heatfrom the worm and wheel drive and the slipping clutch is unsatisfactorybecause of its enclosure in the casing containing the oil bath. It

is an object of the present invention to provide an apparatus of thiskind in which better arrangements are provided for dissipation of heatfrom the slipping clutch.

Accordingly the present invention provides a drive arrangement for acable reeling 'drum comprising a drive shaft, a support member rotatablymounted on the drive shaft but axially fixed in relation thereto, anannular disc member secured to said support member, a drive memberconnected to the drive shaft, a first clutch plate member coaxial withthe drive shaft and axially floating in relation thereto, at least twolinks drivingly connecting said first clutch plate member to said drivemember, said links being so connected that some axial movement of saidfirst clutch plate member relative to said drive member is allowed, asecond clutch plate member coaxial with said drive shaft and axiallyfloating in relation thereto, axially spaced from said first clutchplate member and on the opposite side of said disc member, meansconnecting said second clutch plate member for rotation with the driveshaft so that axial movement of the second clutch plate member isallowed relative to said first clutch plate member and said disc shaft,and means for applying an axial closing pressure between the first andsecond clutch plate members so that the clutch plate members pressagainst the opposite sides of the disc member and provide a frictionaldrive between said drive shaft and said support member, one of saiddrive shaft and said support member being connected for drive from amotor and the other of said drive shaft and said support member beingdrivingly connected to a cable reeling drum.

In order that excessive loads are not imposed on a cable when cablereeling is started it is desirable that the static frictional forces'inthe clutch should not be substantially greater than the dynamic frictionforces. It is also desirable, that the arrangement is capable ofsupplying a constant level of torque during long periods of operation.The present invention seeks to achieve satisfactory results in theserespects by the provision of an arrangement which is intended to ensureadequate and even cooling of the friction surfaces, and by providing foraxial movement of the clutch plates whilst under drive.

The annular disc member is preferably of generally channel-shape intransverse section, with the friction pads of the clutch plates engagingopposite outer surfaces of the member. The heat thus generated isdissipated to air flowing within the member as it rotates. Vanes may beprovided on the inner surfaces of disc member so that air flow isincreased.

The connection between the disc member and the first clutch plate bylinks is of importance since the clutch plate is free to move axiallyeven under load". By allowing for such axial movement wear of the padsduring prolonged operation will not lead to excessive reduction oftransmitted torque. Preferably the means connecting the second clutchplate for rotation with the drive shaft is also constituted by at leasttwo links for the same reasons.

The support member may be a framework having connecting radial spokesbut is preferably an enclosed casing surrounding the drive member andclutch plates. In this way protection against water and grit andcorrosion of the disc member is provided.

A preferred arrangement of the drive includes an annular pressure platerotatable with said drive shaft and coaxial with said clutch plates,means for restraining in at least one direction axial movement of saidpressure plate relative to one clutch plate, and resilient meansarranged between the pressure plate and the other clutch plate, wherebysaid axial closing pressure is applied to the clutch plates. The meansfor restraining axial movement may include an axially adjustableconnection so that the loading applied by the resilient means to theother clutch plate is adjustable. This axially adjustable connection mayinclude interengaged screw-threaded parts. Where a casing contains thedrive arrangement this may conveniently form at least part of the hub ofthe cable reeling drum.

The invention will now be further described, by way of example only,with reference to the accompanying drawings, in which FIG. 1 is atransverse sectional view of the hub of a cable reeling drum,

FIG. 2 is a part-sectional, part plan view on the line II-II of FIG. 1,

FIG. 3 is a sectional view of a detail modification of the hub of FIG.1,

FIG. 4 is a sectional view on the line IV-IV of FIG. 7

FIG. 5 is a transverse sectional view of the hub of another cablereeling drum,

FIG. 6 is a part sectional, part plan view on line VI-VI of FIG. 5, and

FIG. 7 is a plan view of a drive for a cable reeling drum which utilisestwo of the drive arrangements according to the present invention.

FIGS. 1 and 2 show the hub arrangement of a cable reeling drum. Anenclosed hub casing 1 having two parts la, lb, bolted together, isrotatably mounted on a drive shaft 2 which carries a worm wheel (notshown) driven by a worm supported by a motor generally indicated at 3.The cable reeling drum itself is indicated at 101'. The drive shaft 2 ishollow and supports the hub casing 1 by bearing 8 and by bearing 4arranged between the outer end of the shaft 2 and an inner hollowcoaxial shaft 5. The shaft 5 extends beyond the end of the drive shaft 2and has an annular flange 6 welded to its outer end and this flange isconnected to the casing part lb by screws 7. Bearing 8 is arrangedbetween the outer surface of the shaft 2 and the casing part and holdsthe casing against axial movement on the shaft 2.

A spider drive member 9 is keyed to the drive shaft 2 within the casingl and has three outwardlyextending arms 10. Each arm 10 carries a link11 connected to thearm at one of its ends by a ball joint 12. Each ofthe three links 11 is connected at its other end by a ball joint 13 toone end ofa respective pin 14. The pins 14 normally lie roughly at rightangles to the links 11 and have a larger diameter portion 15 and asmaller diameter portion 16. The'portion 16 of each pin passes through abore 17 in a first clutch plate 18 and the pin is held against movementin plate 18 by the ball joint 13 and the shoulder between portions 15and 16 so that the pin cannot move axially with respect to the plate.

A second clutch plate l9-is mounted on the major portions 15 of the pins14 so that it can slide axially on the pins. The clutch plates 18, 19are formed with opposing lobes or extensions 20, 21 respectively on eachof which are mounted friction pads 22, 23 respectively. There are threelobes on each plate and each lobe carries two circular friction pads. Anannular disc 24 is arranged between the lobes 20, 21 with the frictionpads 22 and 23 in contact with opposite sides of the disc. The disc 24is bolted to the hub casing 1 through angularly-spaced bosses 25 formedin casing part la.

Pins 14 have a cap member 26 (equivalent to a pressure plate) slidablymounted on their major diameter portions 15 and the member 26 holdspacks of spring washers 27, which surround the portions 15 and press thesecond clutch plate 19 against disc member 24. A generally annularpressure member 28 surrounding the drive shaft 2 presses the cap member26 against its respective spring washers 27. The pressure member 28 hasa sleeve section 29 which is externally screwthreaded and is engagedwith a corresponding internally threaded section 30 forming part of thefirst clutch plate 18. It should be particularly noted that as a resultof the connection of clutch plate 18 to spider drive member 9 by meansof links 11 and ball joints l2 and 13, the assembly of clutch plates 18and 19 is freely movable axially in relation to drive shaft 2 even underfull load, so that substantially constant pressure may be maintainedbetween friction pads 22 and disc 24 within the service life of thepads.

The pressure member 28 has an aperture 31 which may receive a tommy barfor rotating the member 28 relative to the clutch plate 18 so that theaxial distance between the plate 19 and member 28 can be varied. Thusthe pressure exerted by the friction pads 22, 23 on the disc 24 can bevaried by adjusting the axial distance between the plates 19 and 28 sothat the loading applied by the spring washers 27 is varied. Since bothclutch plates 18 and 19 float with respect to the disc 24 theyautomatically centre on the disc so that substantially equal forces areexerted by the pads 22 and 23.

In an alternative arrangement, also illustrated in FIG. I, the pressuremember 28.is provided with a series of teeth 28' and is rotated byengagement with a pinion 31' which is rotatably mounted in an extensionof the cap member 26. Access to the pinion 31 is gained by means of anaperture (not shown) in the casing member lb.

In operation the drive shaft 2 is driven by the motor 3 in such adirection that the cable reel drum attached to the hub casing 1 tends towind on cable. The spider 9 turns with the drive shaft and the links 1 1transmit the drive to the pins 14 through ball joints 12 and 13. Anadjustable proportion of the torque supplied by the motor is transmittedto the disc 24 (and hence to the cable drum through the casing l) byfriction between the pads 22, 23 and the disc. This frictional force isdependent on the loading imposed by the spring washers 27 which in turnis dependent on the axial distance between the plates 19 and member 28.It should however be noted that the spring washers are of the Bellevilletype and have the characteristic that over a limited range the loadingwhich they impose does not vary very much with their spacing. Thusalthough the distance between cap member 26 and clutch plate 19increases with wear of the pads 23 it is not necessary to make numerousadjustments to maintain the axial closing pressure between the plates.This contributes to the maintenance of substantially constant torquewhich the arrangement seeks to provide. In this arrangement the clutchplates run dry but it may be possible to employ an oil filled casing insome circumstances. The motor 3 drives the shaft 2 at a speed slightlyin excess of that required for maximum speed of revolution of the cablereel necessary to wind in cable without leaving slack in the cable as itis reeled in.

One criterion for determining the loading on the washers 27 is that themaximum torque transmissable to the disc 24 is insufficient to causedamage to the cable, under stationary conditions, when kept undertension by running the motor and allowing the clutch plates 18 and 19 toslip with respect to the disc 24. When slack cable needs to be taken upby the cable drum the clutch still slips and the frictional drive forceson the disc 24 are substantially constant. When cable is being drawn outfrom the reel, the motor may be stopped so that the clutch acts as abrake. The construction is such that there is no excessive change intorque transmitted to the drum when the motor is started under theseconditions. Accordingly, it is possible to switch off the motor whencable is being paid out by the cable drum or when the cable reel is atrest.

It is however possible to continue operation of the motor whilst thecable is being paid out since the present arrangement has improved heatdissipation properties. The heat is mainly dissipated from the disc 24through the bosses 25 to the casing 1. In some circumstances it may beadvisable to have a complete or interrupted annular flange on the casing1 in line with the bosses 25 and in contact with the disc 24 to reduceresistance to heat flow across the joint.

Although the casing 1 preferably serves as the hub of the cable drum thedrum may be in other positions, such as on the opposite side of themotor to the casing. An inner drive shaft (see shaft 5) may thentransmit the drive to the cable drum.

An alternative construction of the hub casing is shown in FIGS. 3 and 4.This construction takes advantage of the fact that heat dissipation isaided by rotation of the hub casing.

Referring to these figures, a disc member 124 is bolted between the twohalves 101a, 101b of a cable drum hub casing 101 by bolts 139. The discmember 124 has two spaced discs 124a and l24b joined by a cir cularflange 1240. The discs 124a, 124b are in contact with friction pads 122,123 which are mounted on clutch plates 118, 119 respectively which arespring loaded as before. The disc member also has a central partition140 which lies parallel to and between the discs 124a and l24b. Thepartition 140 is joined to the discs 124a and l24b by vanes 141 and 142respectively. The partition 140 and vanes 141, 142 extend to the outeredge of member 124 but leave an annular chamher 143 between their innerends and the flanges 124c.

Thus the arrangement provides increased ventilation, and hence coolingof the disc-member 124 since, as the hub casing 101 rotates, aircirculation past the discs 124a and 124b is induced. In one direction ofrotation air passes into the chamber 143 between the disc 124a and thepartition ,140 under the action of the vanes 141 and leaves between thepartition and the disc 124b by action of the vanes 142. Moreover, sincethere are two complete annular areas of contact between the casing 101and the discs 124a and 124b, the heat path to the casing is improved.

It may be possible under some conditions to provide an open hub casingso that direct ventilation of the clutch plate is provided but atpresent it is believed that the added protection against grit and waterprovided by an enclosed casing is of value. An enclosed casing alsoprovides some protection against condensation on the clutch plates anddisc member.

FIGS. 5 and 6 showa further modified hub arrangement for a cable reelingdrum. An enclosed hub casing 50 is assembled in two parts 50a and 50bwhich are held to-gether by means of through bolts 51 which clamp theparts 50a, 50b onto opposite sides of an annular disc 52 having achannel-shape section over most of its circumference. As before, thecasing 50 is rotatably mounted on a hollow drive-shaft 53 and supportedby bearings 54 on an inner hollow coaxial shaft 55 which is connected tothe casing part 50b. The casing part 500 is supported on the shaft 53 byball bearings 56. Access panels 150a, l50b are provided in each of thetwo parts of the casing. A cable drum con-nected to the casing isindicated at 101'.

A spider drive member 57 is connected to the drive shaft 53 by means ofa key 58. The member 57 has two radial arms 59, each of which carries atransverse bolt 60 on which are mounted the two ball joints 61, 62.Drive links 63, 64 are connected to the ball joints 61, 62,respectively, and are connected at their other ends through further balljoints 65, 66 to first and second clutch plate members 67,68respectively. Each clutch member is therefore drivingly connected tothe spider member 57 through two links which allow some axial movementofthe clutch members. The clutch members 67, 68 are formed with threesets of opposing lobes on which pairs of friction pads 69, 70 arerespectively mounted for contact with the disc 52.

The first clutch member 67 is formed with a number of axially extendingarms 71 which connect the main body or plate of the member to a sleeveportion 72 on the distant side of casing 50. The portion 72 isinternally screwthreaded and engaged with a threaded boss 73 ofa majoradjusting gear 74. A minor adjusting gear 75 has teeth engaged withthose of gear 74 and is rotatably mounted on an annular, axiallymovable, pressure plate 76, coaxial with the drive and clutch members.The gear 75 has a central key aperture 77- so that it may be rotated bya tool, thereby rotating the major gear and effecting adjustment of thespace occupied by the spring assembly 79. Axial movement of the pressureplate 76 is guided by a dowel 76a extending from a sleeve part of thepressure plate 76 adjacent the gear 75. The sleeve part of the pressureplate surrounds the sleeve portion 72 of clutch member 67.

Three pins 78 extend axially from the pressure plate 76 and pass throughcorresponding apertures in the second clutch member 68; the pressureplate 76 therefore rotates with the drive shaft 53. Each pin 78 is aloose fit in the plate 76 and is located by means of a circlip which isarranged in a groove in the pin and held between the first spring washerand the plate 76. Each pin carries a packing of spring washers 79 whichurge the first and second clutch members 67 and 68 towards the disc 52.As before, the axial distance between the first clutch member 67 and thepressure plate 76 can be adjusted (by virtue of the screwthreadedengagement) and hence, since both clutch members can ad just their axialpositions relative to the disc 52, the pressure exerted by the pads 69,70 on the disc can be varied. Operation of this modified embodiment isotherwise similar to that of the previous embodiments.

It is to be noted that a continuous section of each annular face of thedisc 52 is in contact with the casing as noted earlier this improves theheat path. This embodiment has the further advantage of providing aparticularly easy way of adjusting the axial pressure on clutch members.

When used in conjunction with an electrical cable the drum 101 isprovided with an aperture so that the stationary end of the cable passesfrom the drum and through the hollow shaft to a connection on thestructure to which the drum is attached. Since the cable tends to rotateas it is reeled it is normally necessary to provide a suitable rotatableconnection for the cable at the inner end of shaft 55. As shown in H6.5, this may be provided by one or more slip rings 80, in contact withbrushes 81. Each slip ring is connected with an appropriate portion ofthe core of the cable and turns with the shaft 55, from which it isinsulated.

A similar arrangement may also be provided with the apparatus of FIG. 1.

Although in the embodiments which have been described the casing hasbeen the means of transmitting the drive directly to the cable drum ithas already been noted that the inner shafts 5 and 55, which areconnected to the respective casings, may be used for this purpose. lnFIG. 7 there is shown an arrangement in which two drive units of thetype shown in FIG. 5 are used in this way.

The casings 50' are each drivingly connected to a common output shaft55'. Associated with each casing is a separate input comprising a motorand gearbox 121. The outputs from the gearboxes 121' are separate andapplied to their respective casings through drive shafts 53' coaxialwith shaft 55'. The complete shaft assembly is supported. inself-aligning bearings 122 (only one shown) and is connected by aselfaligning coupling 123' to the input of a gearbox 124', which drivesa cable reeling drum 125'. The complete arrangement is mounted on aframe member 126 which also supports a slip-ring housing 127' in whichthe necessary rotating electrical interfaces for the'cable connectionsare provided. The cable entry to the housing 127' is indicated at 128'.

By providing two complete drive units (including motor and gearbox)acting on a common shaft it is therefore possible to use standardequipment to supply increased torque requirements in a convenient andeconomical way.

1 claim l. A drive arrangement for a cable reeling drum comprising adrive shaft, a support member rotatably mounted on the drive shaft butaxially fixed in relation thereto, an annular disc member secured tosaid support member, a drive member connected to the drive shaft, afirst clutch plate member coaxial with the drive shaft and axiallyfloating in relation thereto, at least two links drivingly connectingsaid first clutch plate member to said drive member, said links being soconnected that some axial movement of said first clutch plate memberrelative to said drive-member is allowed, a second clutch plate membercoaxial with said drive shaft and axially floating in relation thereto,axially spaced from said first clutch plate member and on the oppositeside of said disc member. means connecting said second clutch platemember for rotation with the drive shaft so that axial movement of thesecond clutch plate member is allowed relative to said first clutchplate member and said disc shaft, and means for applying an axialclosing pressure between the first and second clutch plate members sothat the clutch plate members press against the opposite sides of thedisc member and provide a frictional drive between said drive shaft andsaid support member, one of said drive shaft and said support memberbeing connected for drive from a motor and the other of said drive shaftand said support member being drivingly connected to a cable reelingdrum.

2. A drive arrangement according to claim 1 further including at leasttwo links connecting said second clutch plate member to said drivemember, said links constituting said means connecting said second clutchplate member for rotation with the drive shaft.

3. A drive arrangement according to claim 1 wherein said disc member isgenerally channel-shaped in transverse section, the channel being openoutwardly for entry of air for cooling the surfaces engaged by theclutch plate members.

4. A drive arrangement according to claim 1 wherein said support membercomprises a casing which encloses said clutch plate members and thesurfaces of said disc member engaged by said clutch plate members.

5. A drive arrangement according to claim 4 wherein said casing isformed in at least two parts, said annular disc member being clampedbetween said parts.

6. A drive arrangement as claimed in claim 1 and further including anannular pressure plate rotatable with said drive shaft and coaxial withsaid clutch plate members, a pressure member for restraining axialmovement of said pressure plate away from said first clutch platemember, and resilient means arranged between the pressure plate andthesecond clutch plate member, whereby said axial closing pressure isapplied to the clutch plates.

7. A drive arrangement as claimed in claim 6 wherein said pressuremember and said first clutch plate' member are in threaded engagementcoaxially with said drive shaft for adjustment of their relativeaxialpositions so that the loading applied by the resilient means to theclutch plate members is adjustable.

8. A drive arrangement as claimed in claim 7 including a first gearmember integral with said pressure member, a second gear memberrotatably supported by said pressure plate and in engagement with saidfirst gear member for effecting adjustment of said pressure plate inrelation to said first clutch member.

9. A drive arrangement as claimed in claim 6 wherein the means forapplying axial closing pressure on said first and second clutch platemembers comprises a plurality of pins extending between said pressureplate and said second clutch plate member and a stack of axiallycompressible spring discs mounted on such pins.

1. A drive arrangement for a cable reeling drum comprising a driveshaft, a support member rotatably mounted on the drive shaft but axiallyfixed in relation thereto, an annular disc member secured to saidsupport member, a drive member connected to the drive shaft, a firstclutch plate member coaxial with the drive shaft and axially floating inrelation thereto, at least two links drivingly connecting said firstclutch plate member to said drive member, said links being so connectedthat some axial movement of said first clutch plate member relative tosaid drive member is allowed, a second clutch plate member coaxial withsaid drive shaft and axially floating in relation thereto, axiallyspaced from said first clutch plate member and on the opposite side ofsaid disc member, means connecting said second clutch plate member forrotation with the drive shaft so that axial movement of the secondclutch plate member is allowed relative to said first clutch platemember and said disc shaft, and means for applying an axial closingpressure between the first and second clutch plaTe members so that theclutch plate members press against the opposite sides of the disc memberand provide a frictional drive between said drive shaft and said supportmember, one of said drive shaft and said support member being connectedfor drive from a motor and the other of said drive shaft and saidsupport member being drivingly connected to a cable reeling drum.
 2. Adrive arrangement according to claim 1 further including at least twolinks connecting said second clutch plate member to said drive member,said links constituting said means connecting said second clutch platemember for rotation with the drive shaft.
 3. A drive arrangementaccording to claim 1 wherein said disc member is generallychannel-shaped in transverse section, the channel being open outwardlyfor entry of air for cooling the surfaces engaged by the clutch platemembers.
 4. A drive arrangement according to claim 1 wherein saidsupport member comprises a casing which encloses said clutch platemembers and the surfaces of said disc member engaged by said clutchplate members.
 5. A drive arrangement according to claim 4 wherein saidcasing is formed in at least two parts, said annular disc member beingclamped between said parts.
 6. A drive arrangement as claimed in claim 1and further including an annular pressure plate rotatable with saiddrive shaft and coaxial with said clutch plate members, a pressuremember for restraining axial movement of said pressure plate away fromsaid first clutch plate member, and resilient means arranged between thepressure plate and the second clutch plate member, whereby said axialclosing pressure is applied to the clutch plates.
 7. A drive arrangementas claimed in claim 6 wherein said pressure member and said first clutchplate member are in threaded engagement coaxially with said drive shaftfor adjustment of their relative axial positions so that the loadingapplied by the resilient means to the clutch plate members isadjustable.
 8. A drive arrangement as claimed in claim 7 including afirst gear member integral with said pressure member, a second gearmember rotatably supported by said pressure plate and in engagement withsaid first gear member for effecting adjustment of said pressure platein relation to said first clutch member.
 9. A drive arrangement asclaimed in claim 6 wherein the means for applying axial closing pressureon said first and second clutch plate members comprises a plurality ofpins extending between said pressure plate and said second clutch platemember and a stack of axially compressible spring discs mounted on suchpins.